Newbie: ftp
Date: 16-Jan-00
Author: cogNiTioN <cognition@attrition.org>
ftp:
What is ftp?ftp is a program that allows you to exchange files between your machine, and
a remote one. You can upload files (send them from your machine to the remote
one), or you can download files (your machine receives them from the remote
one). FTP is also the name of the protocol the program uses to transfer the
files (File Transfer Protocol), but in this document, ftp will refer to the
program.
Note: There is more than one ftp program (or client), so this file refers to
the command line utility found on most unix/linux systems. The MS-DOS ftp
program will probably be very similar, and even the basics will be applicable
to most GUI (Graphical User Interface) ftp clients. Modern web browsers, and
even some not so modern ones, are able to download files from ftp sites.
Why use ftp?ftp can be used to upload/download any files to any machine running an ftp
server (or daemon), and on which you have a valid login account, or the server
has a anonymous account anyone can use. e.g. lots of web sites allow you to
upload your page with ftp, and lots of programs/files (including many
distributions of Linux) are available from ftp sites which have anonymous
accounts. Anonymous accounts are accounts that anyone can use, instead of
entering your user name when prompted, to make use of an anonymous account,
you use the name 'anonymous', and normally you get asked to use your email
address as the account password. Normally an anonymous accout has limited
privilages, meaning an anonymous user can only access certain parts of the
site and more often than not, can only download files; they wouldn't be able
to upload them.
While ftp used to be almost exclusively used for uploading files, it is now
losing ground to scp, which uses ssh to transfer the files, and is
thus infinitely more secure. The use of scp is beyond the scope of this file,
but there are plans for a file on scp.
Using ftp:
As with most Un*x programs, there is more than one way to connect to a remote
ftp site. One way is to start ftp and specify the remote machine (or server) on
the command line. Another way is to start ftp, and then use the open command
inside ftp to open a connection.
Note: Once ftp is running, it has it's own special prompt, just like a unix
shell. This prompt will normally look like this 'ftp>'.
(Please note: A fictional ftp site has been used for security reasons)
cog@pingu:/usr/cog $ ftp ftp.attrition.org
Connected to forced.attrition.org.
220 ProFTPD 1.2.0pre3a Server (forced proftpd service) [forced.attrition.org]
Name (ftp.attrition.org:cog): cog
331 Password required for cog.
Password:
230 User cog logged in.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp>
or:
cog@pingu:/usr/cog $ ftp
ftp> open ftp.attrition.org
Connected to forced.attrition.org.
220 ProFTPD 1.2.0pre3a Server (forced proftpd service) [forced.attrition.org]
Name (ftp.attrition.org:cog): cog
331 Password required for cog.
Password:
230 User cog logged in.
ftp>
Now you're connected to your ftp site, you need to know how to transfer
files to (download) and from (upload) your machine to the ftp server.
To upload files from your machine to the server you can use the put and
mput commands.
putlocal-file [remote-file]
Store a local file on the remote machine. If remote-file is
left unspecified, the local file name is used.
[send can also be used, and is a synonym for put]
mput[local-files]
Expand wildcards in local-files given as arguments and do a
put for each file.
e.g.:
ftp> put ftp.file.html
local: ftp.file.html remote: ftp.file.html
200 PORT command successful.
150 Opening BINARY mode data connection for ftp.file.html
226 Transfer complete
ftp> put ftp.file.html ftp.html
local: ftp.file.html remote: ftp.html
200 PORT command successful.
150 Opening BINARY mode data connection for ftp.html
226 Transfer complete
ftp> mput */index.*
mput news/index? y
200 PORT command successful.
150 Opening BINARY mode data connection for news/index.
226 Transfer complete.
442 bytes sent in 0.0835 secs (5.2 Kbytes/sec)
mput news/index.html? y
200 PORT command successful.
150 Opening BINARY mode data connection for news/index.html.
226 Transfer complete.
1377 bytes sent in 0.256 secs (5.3 Kbytes/sec)
mput news/index.old.shtml? n
mput linux/index? y
200 PORT command successful.
150 Opening BINARY mode data connection for linux/index.
226 Transfer complete.
1192 bytes sent in 0.156 secs (7.5 Kbytes/sec)
mput linux/index.html? y
200 PORT command successful.
150 Opening BINARY mode data connection for linux/index.html.
226 Transfer complete.
ftp>
As the above example shows, when using mput, ftp normally asks you before
transferring the files. If you're transferring lots of files, this can get
very tedious, and is time consuming, so I like to start ftp with the -i
flag. This turns off interactive prompting and transfers the files without
asking you. Once at the ftp> prompt, if you type prompt, you can
toggle the status of interactive mode.
If, as in the above example, you are transferring files to any directory other
than the current working directory (which can be found using the pwd
command), then you need to make sure the directory you're transferring files
to already exists, because ftp will not automatically create it for you.
To create directories you can use the mkdir command just as you would in a
normal Un*x shell.
e.g.:
ftp> mkdir /test
257 "/test" - directory successfully created.
Now, to download a file from the remote server to your computer you first
need to locate the file you want to download. One command you may use to do
this is ls, which works the same as the unix version of ls, except
the output is in the format of ls -l. dir can also be used, as
can mdir. dir is a synonym for ls, and mdir is the same as dir,
except that multiples files can be specified with mdir.
If you need to move around directories on the remote machine you can use
the command cd.
Once you've located the file to download, there are several ways you can get
the file; get, mget, reget, recv and newer.
getremote-file [local-file]
Retrieve the remote file and store it on the local machine. If the
local filename is not specified, it is given the same name as it has
on the remote machine.
mget is rather like mput; it is the same as get, except that
wildcards are expanded with mget.
reget also works the same as get, except if the local file already
exists, and the local file is smaller, it assumes that the local file is a
partial download of the remote file and continues the download from the end
of local file. This is good if the transfer is dropped half way through.
newer is again, the same as get, except the remote file is only got if
it is newer than the already existing local file. This is useful for seeing if
a particular package/file has been updated, and then downloading it if it has.
Advanced Usage of ftp:ftp has quite a few 'advanced' functions, which include the ability to
define macros (strings of commands which can be called from just one command),
automatic login (with automatic execution of a macro), file name mapping and
character translation (in filenames). These are all detailed in the man page,
and I will leave them as an exercise for the reader.
------------------------------------------------------------------------
More information:
Man pages: ftpscp
Books: _Linux in a Nutshell_ (O'Reilly ISBN 1-56592-167-4)
available on amazon.com, here.
Any feedback on this file should be directed at me, via an email to:
<cognition@attrition.org>
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cogNiTioN <cognition@attrition.org>
Copyright 1999 cogNiTioN